Fundamentals of Electrical Engineering

Published by McGraw-Hill Education
ISBN 10: 0073380377
ISBN 13: 978-0-07338-037-7

Chapter 2 - Fundamentals of Electric Circuits - Part 1 Circuits - Homework Problems - Page 48: 2.2


Voltage: $JC^{-1}$ Current: $Cs^{-1}$ Resistance: $JsC^{-2}$

Work Step by Step

Voltage is defined as the amount of electric potential energy required to transport one unit of charge from one point to another in a closed circuit. Since the SI unit for energy is the Joule ($J$) and that for charge is the Coulomb ($C$), the SI unit for voltage is Joules per Coulomb ($JC^{-1}$). Current is defined as the amount of charge passing through a point in a closed circuit per unit time. Since the SI unit for charge is the Coulomb ($C$) and that for time is the second ($s$), the SI unit for current is Coulombs per second ($Cs^{-1}$). Resistance is defined as the ratio of voltage applied to a point in a circuit to the amount of current flowing through it. Having obtained the SI units for both voltage ($JC^{-1}$) and current ($Cs^{-1}$), by Ohm's Law of $V=IR\Rightarrow{R}=\frac{V}{I}$, the SI unit for resistance is Joule seconds per Coulomb squared ($JsC^{-2}$). This is commonly known as the ohm ( $\Omega$).
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